While it can't stay in the air for days and circumnavigate Kerbin 40 times, the Wheesely has enough fuel to get where you need to go and make a few detours on your way back. It also features a comprehensive suite of science experiments, as well as the amenities for accessing and resetting them. A reasonably high cruising altitude, stable flight under physics acceleration, and acceptable trans-sonic behavior also means that you don't have to wait 4 hours to get anywhere.

Here's a picture dump from a single orbital flight in my very heavily modded KSP install #3. The primary focus is on realism and graphics. Such graphics... never have I seen KSP this pretty it beats some AAA games I've seen! Album.
Here's one image to tempt you into looking at the rest: